Conventionally, an optician performs an adjustment of the frame directly on the face of the wearer, manually, depending on indications of comfort that the wearer provides him with and know-how gained from experience.
This adjustment is long and tedious for the optician and the wearer, and its quality, which is important for the visual correction, depends on the operator and the care taken performing this operation.
It is often carried out on reception of the finished pair of spectacles, i.e. in which the ophthalmic lenses have been mounted.
Therefore, this process does not always allow a pair of spectacles to be produced the optical and mechanical characteristics of which are precisely adapted to the wearer.
A method for determining characteristics of a frame so that they are perfectly adapted to the face of the wearer is especially known from document U.S. Pat. No. 4,762,407, this method providing one possible solution to this problem.
In the method proposed by this document, the ideal placement in front of the eyes of the wearer of ophthalmic lenses providing the visual correction required by the wearer is firstly determined. Next, the geometric characteristics of the frame allowing this ideal placement of the ophthalmic lenses in front of the eyes of the wearer are determined depending on the shape of the face of the wearer. Lastly, the frame is constructed so as to have the determined geometric characteristics.
However, this method does not allow a predetermined frame, which has already been assembled, to be adjusted to fit on the face of a wearer in the absence or presence of ophthalmic lenses.